A modern air conditioner used in cooling a building requires four basic operations: 1) a refrigerant fluid such as Freon® in gaseous phase is compressed. This compression heats the fluid. 2) The hot pressurized fluid is then passed through a heat exchanger located outside the building where it is cooled. 3) The fluid is then allowed to expand or evaporate. This depressurization contributes to further cooling the fluid. The depressurized cold fluid is then passed through a second heat exchanger located inside the building where it is allowed to absorb heat thereby cooling the inside of the building.
In the past, air conditioners and refrigerators have used fluids such as ammonia, chloromethane, and sulfur dioxide. However, these substances are toxic and their use is problematic. Newer fluids including the chlorofluorocarbon (CFC) such as Freon® are non-toxic but have been shown to destroy the ozone layer. The Montreal Protocol on Substances that Deplete the Ozone Layer classifies Freon-11 and Freon-12 as Annex A substances and bans their production and consumption as of 1996.
The interim replacements for CFCs are hydrochlorofluorocarbons (HCFCs). Even though these compounds contain chlorine they deplete stratospheric ozone to a much lesser extent than CFCs. Yet, these fluids present another problem: they are super greenhouse gases and, molecule for molecule, they can trap infrared rays hundreds to thousands of times more efficiently than carbon dioxide.
One possible solution is to avoid the use of such fluids entirely, and to use air as a refrigerant fluid. Air cycle air conditioners are described in U.S. Pat. No. 2,586,002 by Carson et al, U.S. Pat. No. 3874,188 by Zara et al, U.S. Pat. No. 4,015,438 by Kinsell et al, U.S. Pat. No. 4,127,011 by Giles et al, U.S. Pat. Nos. 4,535,606 and 4,550,573 by Rannenberg, U.S. Pat. No. 4,553,407 by Rannenberg, U.S. Pat. No. 5,121,610 by Atkinson et al, U.S. Pat. No. 5,373,707 by Ostersetzer et al, U.S. Pat. No. 6,041,615 by Ostersetzer et al, U.S. Pat. No. 6,301,922 by Ochi, U.S. Pat. No. 6,381,973 by Bhatti, U.S. Pat. No. 6,484,528 by Piao, U.S. Pat. No. 6,966,198 by Piccirilli, U.S. Application 2005/0126204 by Piccirilli.
No air cycle air conditioner described in the prior art, however, offers the economy, reliability, efficiency and environmental sustainability of the present invention. Further features, aspects, and advantages of the present invention over the prior art will be more fully understood when considered with respect to the following detailed description and claims.